Early Warning System for Douglas-Fir Tussock Moth Outbreaks in the Western United States

Abstract

Abstract The Early Warning System is a pheromone-based trapping system used to detect outbreaks of Douglas-fir tussock moth (DFTM, Orgyia pseudotsugata) in the western United States. Millions of acres are susceptible to DFTM defoliation, but Early Warning System monitoring focuses attention only on the relatively limited areas where outbreaks may be developing. During 20+ years of monitoring, the Early Warning System provided warnings of 1–3 years for seven of nine outbreaks. No warnings were provided for two outbreaks because of inadequate density and distribution of Early Warning System plots in those specific areas. Plots should be evenly distributed over host-type forests at a density of at least 1 Early Warning System plot per 3,000 ac. After potential outbreaks have been identified by the Early Warning System, ground sampling for egg masses and larvae is necessary to characterize local DFTM populations. West. J. Appl. For. 19(4):232–241.